It has been discovered that the medical outcome for a patient suffering from severe brain trauma or from ischemia caused by stroke or heart attack is improved if the patient is cooled below normal body temperature (38.degree. C.). As understood by the present invention, the medical outcome for many such patients might be significantly improved if the patients were to be moderately cooled to 32.degree. C.-34.degree. C. relatively quickly after an ischemic insult for a short period, e.g., 12-72 hours. It is believed that such cooling improves cardiac arrest patient outcomes by improving the mortality rate, in that many organs can benefit from the cooling, and by improving the neurological outcome for those patients that survive.
Systems and methods have been disclosed that propose cooling blood flowing to the brain through the carotid artery. An example of such systems and methods is disclosed in co-pending U.S. patent application Ser. No. 09/063,984, filed Apr. 21, 1998, owned by the present assignee and incorporated herein by reference. In the referenced application, various catheters are disclosed which can be advanced into a patient's carotid artery and through which coolant can be pumped in a closed circuit, to remove heat from the blood in the carotid artery and thereby cool the brain. The referenced devices have the advantage over other methods of cooling (e.g., wrapping patients in cold blankets) of being controllable, relatively easy to use, and of being capable of rapidly cooling and maintaining blood temperature at a desired set point.
As recognized in co-pending U.S. patent application Ser. No. 09/133,813, filed Aug. 13, 1998, owned by the present assignee and incorporated herein by reference, the above-mentioned advantages in treating ischemia by cooling can also be realized by cooling the patient's entire body, i.e., by inducing systemic hypothermia. The advantage of systemic hypothermia is that, as recognized by the present assignee, to induce systemic hypothermia a cooling catheter or other cooling device need not be advanced into the blood supply of the brain, but rather can be easily and quickly placed into the relatively large vena cava of the central venous system. Moreover, since many patients already are intubated with central venous catheters for other clinically approved purposes anyway, providing a central venous catheter that can also cool the blood requires no additional surgical procedures for those patients. A cooling central venous catheter is disclosed in the present assignee's co-pending U.S. patent applications Ser. Nos. 09/253,109, filed Feb. 19, 1999 and 09/305,613, filed May 5, 1999, both of which are incorporated herein by reference.
The present invention understands that the above-mentioned benefits of hypothermia might be particularly suited for treating cardiac arrest. This is because outcomes for cardiac arrest patients currently are very poor, even when the patients can be resuscitated, since brain damage occurs as a result of the global ischemia caused by lack of blood flow before resuscitation. The severity of such brain damage, as understood herein, can potentially be alleviated by hypothermia.